The powders, such as pigments, used in the make-up cosmetics currently generally supplied to the market, especially those of the loose or solid type, are usually complex oxides and are endowed with hydroxy groups on their surface, with the amount of the hydroxy groups differing depending on the types of the powders. In titanium oxide powders, as a typical example of these powders, there exists a minor amount of weakly reactive hydroxy groups or adsorbed water as demonstrated by the analysis of the moisture produced on heating, with the moisture content of the water-containing titanium oxide ranging between 15 to 30 wt %. The powders, such as pigment powders, differ in their degree of surface hydrophilicity or lipophilicity according to the types of the powders, while there co-exist various powders having different degrees of surface activity. In addition, the reason why the makeup finish tends to be transparent or uneven or to exhibit insufficient tight-adhering feel may be thought to reside in (a) change in the particle size or deformation in particle shape due to mechanical impact on the minute surfaces, difference in wetting by secretions such as water, perspiration or sebum due in turn to the difference in surface activity caused by freshly produced surfaces; and (b) the difference in the amount of the oily agent physically affixed or adsorbed with a non-uniform weak force on the powder surface or in the HLB of the oily agent, or the segregation of the oil contents due to mechanical impact in the course of the preparation. That is, conventional cosmetics are subjected to flocculation or changes in the refractive index of the cosmetic powders on account of changes in wetting of the powders by water, perspiration or sebum, and hence to uneveness or makeup dry of makeup finish, which are counted for disadvantages in the art.
The following methods and cosmetics are known in the art as means to overcome these deficiencies:
i) The method of surface treatment of the powders with surfactants;
ii) the method of surface treatment of lecitin or N-stearoyl-aluminum L glutaminate;
iii) the method of heat-treating the powder surface with methyl hydropolysiloxane;
iv) the method of processing the powder surface with alcoholic compounds; and
v) "Cosmetics mainly consisting of cosmetic powders and a coloring agent characterized in that the cosmetics are admixed with cosmetic powders and/or coloring agent treated with a water and oil repellant agent consisting of a fluorine containing polymer" according to the JP Patent Kokoku Publication (JP-Kokoku) Go. 61-55481/1986, and "Cosmetics mainly consisting of cosmetic powders and/or a coloring agent characterized in that the cosmetics are admixed with cosmetic powders and/or a coloring agent surface-treated with a fluorine-containing resin, according to JP Patent Kokoku No. 61-48803/1986.
The above cited conventional technology has however the following disadvantages.
(i) The method of surf ace treatment of the powder with metal soap-surfactant.
The cosmetics treated with metal soap such as aluminum stearate, zinc stearate or zinc myristate is water-repellant, but is not oil-repellant. Thus the cosmetics are not resistant to sebum and become uneven due to exuded sebum. The cosmetics also become no longer water-repellant depending on selection of surfactants. The cosmetics are similar to metal soap as long as the resistance to sebum or fat is concerned.
These agents are simply affixed or adsorbed physically to the powder surface and hence may be affixed or adsorbed unevenly or inferior in water repellancy depending on the production method employed.
(ii) The method of surface-treating the powder surface with lecitin or stearoyl-aluminum L-glutaminate.
The cosmetics exhibit affinity to skin and some water and oil repellancy but only to a lesser extent. More over, since surface treatment agents, such as lecitin, are adhered physically to the powders, the surface treatment agents tend to become desorbed from the powders under the strong shearing force caused by the mechanical force in the course of the production process of the cosmetics, while the makeup finish tends to become transparent by water or perspiration or be subjected to shine of makeup finish due to sebum.
(iii) The method of heat-treating the powder surface with methyl hydropolysiloxane.
Silicon oils exemplified by methyl hydropolysiloxane are satisfactory in water repellancy, but are rather inferior in oil repellancy. The commercial cosmetics, produced by reacting the silicon oil with hydroxy groups on the powder surface, are somewhat inferior in water repellancy and practically nil in oil repellancy. It is because a number of hydroxy groups and hydroxy groups of methyl hydropolysiloxane remain unreacted and only a few of these hydroxy groups take part in chemical bonding.
(iv) The method of treating the powder surface with alcoholic compounds.
The method is effective to protect the hydroxy groups on the powder surface. Although the produced cosmetics are improved as to the tendency to become transparent due to wetting, they are only low in adhesion to skin and the makeup finish tends to become uneven.
(v) The surface-treated cosmetic powders in the cosmetics produced in the JP Kokoku Nos. 61-55481/1986 and 61-48803/1986 are inferior in water and oil repellancy, with only a few group of the powders and the surface treatment agent taking part in the reaction. The cosmetics containing pigments free of hydroxy groups, such as titanium oxide, are entirely unsatisfactory as to the water and oil repellancy since the groups taking part in chemical bonding are substantially nil.